- Created by: emhpalmer
- Created on: 29-05-14 18:38
Factors Influencing EB: Culture
"Skinny = Beautiful" recent idea in Western culture (Last 40 years)
In many cultures, being voluptuous and curvy is attractive as it's a sign of health and plentiful resource in times of scarcity. There's a certain pride in gorging, it signifies wealth and status.
- African cultues plump females = wiser + more fertile
- Asian cultures weight = affluence + success
- Hawaiian/Samoans larger size = beauty + status (in both genders)
Factors Influencing EB: Culture 2
Wardle et al (1997):
Evaluated the diets of 16000 young adults across 21 EU countries
- Sweden, Norway, Denmark, Holland- Fibre high diets
- Spain, Italy and Portugal- Fibre low diets, but high in fruit. (Hotter less energy needed to keep warm)
- England and Scotland- low in fruit
Factors Influencing EB: Culture 3
Bedouin Arab women living in the desert had little variation with those living in urban environments but ate more carbs and protein, as well as a higher salt intake than Jewish women living in urban areas.
Factors Influencing EB: Parents
After the ages of 3 or 4 food preferences are no longer determined by a biological need and begin to be influenced by environmental cues and external factors.
Skinner et al found that children as young as 2 had preferences like their mother
Birch: The food in the home is what will be liked because it's limited to what's there, rather than direct link to mother's preferences
Factors Influencing EB: Parents 2
Social learning theory:
Duncker (1938)- found that children were more likely to try a new food tried by mother, rather than by another model like another child or unfamiliar adult.
Implication: unfamiliar foods are less likely to be eaten without a cue from parent, possibly to avoid dangerous foods
Factors Influencing EB: Parents 3
Natural animal instinct to survive by avoiding poisons that could be found in unfamilar food.
The more familiar we are with a food the more we like it:
Birch & Marlin (1982) found that between 8 and 10 exposures to a new food would have a significant effect on our preference, enough to shift it from disliking to liking.
As we try new foods our preferences change, other factors are involved not just parents, familiarity is important too.
Factors Influencing EB: Parents 4
Tibbs et al (2001)- positive correlation between low-fat eating patterns and low dietary fat intake with parents intake and model of healthy eating behaviours. (Better parental diet model better child diet later in life)
Though this may be due to same food available in the same house so diet has to be the same, in addition, parents cook for children so eat the same food. No choice rather than copied behaviour.
Olivera et al (1992) also found a correlation between mother and child food intake -> Implying that to improve a child's diet you start with mother/parent. (Healthy eating in school programs, need to be effective at home too)
Early awareness of healthy diet may also be influential in dietary preferences.
Factors Influencing EB: Peers
Normative Social Influence:
Need to be liked! Wanting to be accepted into a certain group by liking certain foods or omitting certain foods.
Feunekes et al (1998) found that 19% of food consumed by adolescents was similar to that of their friends.
This may be to fit in, or possibly because it acts as further reassurance that food is familiar, safe and tasty, so influences our perception of the food and willingness to try the food.
19% is not that significant, and could just be similarities in diet due to culture or social reasons rather than direct peer influence. Other factors have a role.
Factors Influencing EB: Mood
Food <=> Mood
Our mood is an internal cue. We may be encourage to eat certain foods or extreme quantities of food: to encourage positive or counteract negative emotions.
E.g. chocolate to feel happy
Davis et al (1988) found that bulimia-nervosa is strongly associated with feelings of anxiety before a binge, implying that depressed or anxious mood could trigger binge-eating as a form of immediate gratification.
Factors Influencing EB: Mood 2
The Serotonin Hypothesis
Theory that depression is caused by low levels of the biochemical: serotonin. It is then thought that serotonin suppliments combat the deficieny and lift mood. Certain foods contain antidepressant properties, like chocolate which contains tryptophan which is responsible for creating serotonin.
Parker et al (2006) found that as an emotional eating strategy, eating chocolate would prolong negative feelings rather than counteract them.
Factors Influencing EB: Mood 3
The Opiate Hypothesis
This theory links the body's reward system and food.
Pleasure is released via endorphins, when certain foods are ingested (that we enjoy) trace amounts of opiates are rleased to reinforce the eating of the food. Foods are perceived as tastier than others due to higher amounts of endorphins being released, and so greater pleasure we receive.
The perception of a happier mood after eating chocolate may be as a result of the endorphins released from eating it rather than an increased level of serotonin.
However it may be that learned associations and consequences of eating certain foods leads to expectations that we fulfil rather than actual effect of the food. Chocolate is branded as a feel good food, as are other carbohydrates and sugars so we expect to feel happier after eating them. Lke a placebo effect, we are uplifted because we expect to be uplifted.
Factors Influencing EB: Mood 4
Mood can affect what we eat or even if we eat.
Unhappiness or stress may lead us to not want to eat.
However, many students have reported sequences of binge-eating during exam periods due to stress. Suggesting when our body is trying to cope with stress we eat more to gain more energy, to fight off whatever danger or stressor is causing the anxious feelings.
Factors Influencing EB: Religion
Alongside culture, religion can determine what foods we eat.
In many religions certain foods are not permitted to be eaten:
- In Islam pigs are sacred and so pork is not acceptable to eat
- In Judaism certain parts of animals are not eaten
- Hindus believe cow is a sacred meat so do not eat beef or other cow meat product
In addition religions have festivals that encourage larger quantities of eating or reversley not eating:
- Ramadan is a time when muslims fast until it ends and is celebrated by a large feast and eating together
Factors Influencing EB: Conclusion
It is unclear which factors have the greatest influence, or whether there is a dominating factor. It is possible that many factors are interlinked to contribute to eating behaviours and preferences for food.
Individual differences are too great to determine what has the greatest effect on our diet.
Factors Influencing EB: Culture 4
Research into eating behaviours and preferences is culturally biased. Research is often conducted in Western and or industrialised societies where there is an option to pick and choose food.
Unlike in the developing world whose issues are whether there is food available.
Successes and Failures of Dieting: Intro
At any one time 40% of the female population is trying to lose weight, by dieting
The dieting industry aims at women and girls and has grown over the last 20 years to be a multi-million pound industry.
Successes and Failures of Dieting: Why diet?
Health, self-esteem, body dismorphia (perceiving body image as different to what it actually is)
Media- images of women have become slimmer over the last 50 years. Want to match "ideal" shape and size.
Family- Relationship between mother and daughter's body dissatisfaction and weight concerns. Mother may acta s the model, or could be complex product of relationship (Inconsistent research)
Ethnicity- Mixed reseatch some found higher in white/western women and some more in black and/or asian. Frequency of ED is proportional to their exposure to western media.
Social class- AN found more frequently in higher-class social groups, more sensitivity to body dissatisfaction. (More money, more food, more concerned about appearance) Though research suggests concern of size and ED are more spread across society
Peer groups and social learning- Dieting may be a nrm for a group of friends, further rewarded by compliments and notes about sticking to diet, each encouraging each other. (not Ogden)
Successes and Failures of Dieting: Does it work?
No, some cases of success and maintained weight loss.
Mann et al 2007 most actually eat more on their diet
The boundary model: Herman and Polivy (1984)
Restrained eaters/ dieters: have a larger gap between hunger and satiety. It takes more food to feel full. Dieters set a cognitive boundary that they eat to, but once this is breached then the "What the hell" phenomenon takes place and they eat to satiety- the physiological boundary.
Unrestrained eaters: Eat to satiety (physiological boundary)
Successes and Failures of Dieting: BM eval
Supported by Herman and Mack (1975)- Preload/ taste tast
Two groups: High-restraint (dieters), low-restraint (non-dieters)
Positive correlation between restraint score and amount of food eaten after the preload (milkshake)
Eval of preload: Methodological (questionnaires) Done before to avoid demand characterisitcs, small group sizes (inidividual differences- like or dislike for ice cream or milkshake), Correlational research causality issues, ethical issues (degree of coercion pps received course credit for taking part) Deception to be valid, but followed up and debriefed.
Eval of BM:
- Combines physilogical with psychological
- Lab conditions = high reliability
- Low eco-validity (lab controlled)
- No specification of the cognitive and emotional processes that lead to "what the hell"
Successes and Failures of Dieting: Issues
- Restrained thought rebound: denying the importance of food by trying not to think about it, causes more thought about it. People overeat as a rebound effect of trying to surpress thoughts of food.
- Depression/ lowered mood: Food can lift mood, lack of food lower mood, makes it harder. Feeling useless if break diet, and "what the hell" kicks in.
- Physiological fight back: Body constantly trying to restore set point by increasing feelings of hunger, reduction in base metabolic rate (BMR). Lower BMR means less energy is used up as quickly making weight loss slower, slow weight loss reduces motivation
Mann et al (2007) between 1/3 and 2/3 of dieters gain more weight than lost on diet. Yo-yo dieting (repeated attempts) increases chances of heart disease
Successes and Failures of Dieting: Success!
Powell, Calvin & Calvin (2007):
Lifestyle changes = maintained weight loss
- Physical exercise
- Group & individual support
- Self monitoring: Diary and record of progress (Control and motivated!)
- Low-calorie diets
Realistic goals are vital! The average weight loss is 7lb sustained over 2 years and has benefits for those who are overweight.
Successes and Failures of Dieting: Medicines
- Orlistat- Prevents the absorption of fat from the intestine. Produces substantial weight loss but unpleasant side effects: intestinal discomfort and oily faeces.
- Sibutramine- acts on serotonin pathway involved in regulation of food intake. Significant weight loss, side effects: high blood pressure
Quick fix, not really lifestyle change that benefits in long term, doesn't tackle psychological aspects of dieting. Only recommended when obesity is a serious threat to health.
Dangers with drugs: Rimonabant withdrawn from Europe over concerns of it leading to anxiety and depression.
- Gastric band- band around the stomach reduce its size, less food to feel full
- Gastric bypass- a tube inserted at the top of the stomach that reduces stomach size
Dangers with surgery: abscess, pneumona and other lung infections, 2-4% mortality rate
Biological Explanations for EB: intro
Controlling eating and satiation:
Homeostasis- The maintenance of a constant internal environment
Our diet alows homeostasis as it provides nutrients that allow physiological processes to be regulated in narrow limits.
Biological Explanations for EB: Stomach
Cannon and Washburn (1912)
Washburn swallowed a deflated balloon which was then inflated in the stomach. Measured stomach contractions in relation to washburn's feelings of hunger
Found negative correlation, decreased levels of hunger as stomach was expanded/fuller
Implies: Presences or absence of food signals to brain when to feed
Cancer of the stomach can mean parts are removed but people are still able to regulate food intake as usual so other mechanisms are involved not just the stomach
Biological Explanations for EB: Dual control hypot
Two (dual) areas of the hypothalamus work together to regulate food intake by giving hunger or satiated signals.
Ventromedial hypothalamus (VMH)- "Satiety centre" Signals of food intake, VMH activated, full feelings causing feeding to stop.
Hetherington and Ranson (1942): lesions on the VMH in rats cause over-eating
Lateral hypothalamus (LH)-"Feeding centre" cue for feeding after decrease in nutrient levels detected, LH activated, hunger signals cause feeding to start.
Anand and Brobeck (1951): Lesions on the LH in rats led to loss of feeding behaviour (Aphagia)
But, animal research might have a different effect on humans. Also how precise are the lesions, just VMH and LH damaged?
Adaptive- to be successful has to be adaptive, theory has to be able to anticipate and prevent hunger, bio does not do this only responsive!
Biological Explanations for EB: Ghrelin
Appetite signal, it's a hormone that is secreted from the stomach in an amount directly proportional to the emptiness of the sotmach.
Cummings et al (2004) Changes in blood ghrelin levels between meals.
6 pps, eat at lunch and ghrelin levels measured every 5 mins, til they requested a meal. Assessed degree of hunger every 30 mins. Ghrelin levels- lowest 70 mins following eating til full. Slow rise, peaking at request for meal. 5/6 pps hunger correlated with ghrelin levels.
- Isolated from time and contect cues, meant changes were due to ghrelin not automatic or learnt responses to time
- Supports work into ghrelin
- Small sample sizes- all male, not representative!
- Correlational- causality issues
- Ethical issues- catheter insertion for blood samples (volunteer, informed consent and debrief)
Biological Explanations for EB: Glucostat Theory
Hunger varies with high or low blood sugar levels.
They do respond rapidly to food intake but actually do not vary much under normal circumstances not enough to signal hunger/ satiety.
Diabetics suffer long-term high blood glucose but have normal appetites.
Biological Explanations for EB: Set Point
Everyone has a certain metabolic set point, a centain weight that they are geared towards, we may fluctuate around it but generally where we return to.
It is determined by hypothalamus, metabolism or rate at which they burn calories. Varying set points per person, they can change when influenced by eating patterns and exercise. The hypothalamus triggers hunger pands during diets (low leptin = hunger)
Obese may have higher set points and those underweight might be geared to a lower set point.
Determined by energy consumption and expenditure.
Eval: Determined by genetics, reductionist and deterministic ignores environmental factors and free will to change (diet and exercise)
Biological Explanations for EB: Evaluation
Reductionist- ignores free will to lose or gain weight, some people can change drastic weight
Other psych exp: Stress, habit of eating food (food is good for energy for processes) habit of eating at times of the day so expect to feel hungry, availability of food has an impact of regularity, quality and quantity of what we eat. Smell and other senses can trigger hunger, a good smell might make us want to eat something.
Ignores environement- Do we just learn to eat regularly? (But: Natural instinct to eat)
Other bio theories- heat production theory that we eat more in winter because eating produces heat (Hara, Brobeck), insulin theory- higher insulin means greater hunger (Helles), fatty acid theory- When higher levels of fatty acid are detected then hunger pangs are triggered (because fat cells are being broken down relying on spare store, glucose theory- more glucose means less hunger (blood transfusion in dog, led to stopping of stomach contractions, suggests not hungry, as blood came from high glucose blood dog)
Biological Explanations for EB: Evaluation 2
Learnt response- Pinel (2007) Scheduled eating in Western countries, the digestive system starts preparing itself by releasing saliva and enzymes just before meal time
Dual Control Hypothesis-
Winnet et al (1990) found that focused lesions to the LH in rats did not cause feeding to stop, but when larger lesions were made the rats ate less. Suggesting that LH alone may not be responsible for feeding. Larger area of brain or multiple mechanisms involved. Sakurai et al (1998) found LH not eating centre but part of control of EB. Damage to LH also causes defecits in thirst and sex.
Gold (1973) Lesions to VMH alone did not cause over eating (hyperphagia) Paraventricular nucleus also damaged caused this. (Replication issues)
Neuropetide Y-> Wickens (2000) found when injecting NPY into rats the immediately began feeding even when satiated.
Eval: Marie et al (2005) mice with no NPY had no decrease in feeding
Evolutionary explanations for food preference
Pre-agricultural socieites- food was limited/ so to make most use of availability of food we used to 'binge-eat' store as fat and survive off that. Ate plenty of sweet, fatty and salty foods when available as they had plenty of energy.
Binge-eating still occurs today even in western or developed society where food is plentiful and expenditure of energy is less (escalators, cars and lifts)
No longer serves a survival purpose.
Fozano and Loque (1992) found a correlation between deprivation and decreasing levels of self control
Higher metabolic rate means more impulsive eating, easier we get through food the more we need to sustain ourselves. Less picky when food is scarce!
Specialised to eat meat-> Teeth evolved to chew meat easier, and a long duodendum and small intestine to aborb protein, chimps are adapted to eat nuts and fruit
Developed weapons and cooperation to survive as a society and further develop language etc.
Garcia & Koelling (1966) rats study, drinking flavoured water = ill, drinking plain water = electric shock. Easier to associate illness with taste and audiovisual events with the shock.
Short gap and repeated trials are needed to form association.
We avoid foods that make you ill to increase survival rate.
Avoiding foods that are unfamiliar, stick to safe foods and avoid potentially harmful ones.
Babies and young kids have a narrow preference for food, especially vegetables like broccoli and sprouts which do contain chemicals that are toxic to the very young- Nesse and Williams (1994)
Embryo protection hypothesis (Profect, 1992)-
Morning sickness whilst babies organs are developing, they can be easily damaged by certain foods. Coffee, tea, meat, alcohol, eggs and veg trigger sickness (Buss, 2008) we are sick because we reject foods that could harm baby.
Taste- Harris (1987) newborn babies prefer sweet things and dislike bitter. Universal preference/disliking. Early mammals were frugivores- sweet taste gives us pleasure (dopamine) as a reinforcer. Poisons have a strong bitter taste- survival reflex.
Unhealthy- Burnham and Phelan (2000) preference for fatty foods helped us survive at times of scarcity. Evo-hangover as food is now plentiful and cheap. Fatty foods are energy rich and help keep us warm, useful in survival. Still eat lots now incase food shortage of energy rich food.
Spice- Sherman and Hash (2001) 7000 recipes from 36 countries- meat dishes had more spice than veg. Spice helped prevent bacteria on meat and keep for longer, especially in hotter climates. Hotter climates = spicier food.
Green banans/Mouldy bread- We avoid unripe or mould foods due to passed on knowledge that it makes us ill (wasted energy) or dead.
Evaluation of evolutionary explanations
Reductionist- doesn't consider free will to try new food and have individual likes/dislikes
also ignores cultural or social influences
Eating disorders- Anorexia Nervosa
Characteristics of AN:
- Refusal to maintain a normal body weight- weighing less than 85% of expected body weight
- Anxiety of gaining any weight or the thought of it.
- Body-image distortion- belief that you're overweight even when very very thin, refusal to accept seriousness of the condition
- Amenorrhoea- stopping of menstruation due to low body weight, missing 3 periods in a row is a clinical characteristic
1 in 250 females aged between 15-30 are affected by AN ,1 in 2000 males aged between 15-30 are affected by AN
90% of cases are female and all cases are resistant to treatment
8% mortality rate from AN, mainly due to suicide
AN effects 0.3 percent of males and 0.9 percent of females- Polivy and Herman (2002)
AN restricting/ AN binge eating: refusal to eat/ episodes of binge-eating followed by purge with significant weight loss (Not the same as BN due to loss in weight)
Eating disorders- AN Bio
Bio explanations: (neural + evolutionary)
Genetics- Holland et al (1988)
Twin study- 45 pairs of twins with at least 1 AN twin 56% concordance rate in MZ twins and 5% for DZ
If genetic it'd be 100% current concordance could be due to environmental factors or shared experiences
Guisinger (2003) hunter gatherer ancestors had to move rapidly with lack of food. Adapted to have little food but a lot of energy. Some AN show that starvation can lead to high levels of restlessness and energy, despite little food.
Eval: Maladaptive behaviours should decrease as we evolve but AN is on the rise- other factors are involved
Eating disorders- AN Bio 2
Hypothalamus- Lesions to the LN or lack of blood to this area causing aphagia.
Serotonin- Kaye et al (2005) Brain imaging scans found AN had signif differences in serotonin compared with control group. High serotonin causes anxiety, could be caused by eating amino acids stimulate serotonin, not eating eases anxious feelings. Same before and aftwer weight gain, cause and effect questioned? Symptom of AN or cause?
Dopamine- Kaye et al (2005) used a PET scan of 10 women recovering from AN, and 12 healthy women. In AN women they found overactivity in the basal ganglia- where dopamine interprets pleasure and harm. AN find it difficult to associate good feeling with pleasureable things due dopamine problems.
Birth complications- Premature birth and AN linked; hypoxia (lack of oxygen) impairing neurodevelopment. AN mother breastfeed baby exposes baby to AN and inadequate nutrition. Season of birth- Spring and AN, possible intrauterine infection furing pregnancy. No season effect in hot all year countries, AN still present.
Eating disorders- AN Bio Eval
Many studies are correlational hard to draw cause and effect, not necessarily one causing the other could be a third factor.
Serotonin treatment is ineffective at curing AN
Eating disorders- AN Psych
Psychodynamic: Hilde Bruch (1973)
- Reaction to sexual abuse- Self-loathing (for appealing to the abuser) AN is a self destruction.
- Reluctance to take on adult responsibilities- AN prevents females from developing hips and breasts, remain child like and dependent on parents (What about AN in males?)
- Reflection of low self-esteem- If a person believes they are in some way wrong they deny food as they do not feel deserving. (Perhaps escalation from diet)
- Battle against controlling parents- Bruch (1978) parents of AN are domineering AN is an attempt to regain control by manipulating one thing they control- their body.
- Ineffective parents- failure to respond effectively to child's needs, e.g. wrong response to crying, child becomes confused about internal needs. Adolescence brings desire for autonomy, but takes control to extreme.
Eval- Lacks empirical evidence as not everyone with AN experiences sexual abuse or domineering parents, in addition, deterministic not everyone with sexual abuse or domineering parents develops AN.
Controlling parents observed as controlling over AN meds rather than giving AN control- Steiner et al (1991) This might be to ensure that they take AN rather than being controlling
Eating disorders- AN Psych 2
- Classical conditioning- Leitenberg et al (1968) AN learnt from associations of eating with anxiety- to phobic levels. Losing weight/not eating reduces anxiety.
- Operant conditioning- Praise for losing weight is positive reinforcement for food avoidance. Gilbert (1986) AN feel pleasure and pride from not eating. Guilt is a negative reinforcer for eating and gaining weight attracts negative attention.
- Role of the media- "Thin is beautiful" perpetuated. Keel & Klump (2003) AN found in all countries, explored in the study, but more so in those with heavier westernised influences. Other influences as well as Western media. Becker et al (2002) naturalistic experiment used teen sample from Fiji where a community was introduced to Western TV. Measured AN rates. High development of AN with TV than without. But no direct link or official diagnosis.
- Life events- 14% of AN had experienced negative LE in the 3 months prior to onset. No controls did. Correlational and only 14% still low, other causes.
Eating disorders- AN Psych 3
- Ethnicity- Grabe and Hyde (2006) Meta-analysis of 98 studies found that African-American females reported signif lower body disatisfaction than caucasian and hispanic females. (Possibly due to cultural variations in perception of large body size)
- Peer influences- Dieting common among friends relates to unhealthy weight control behaviours such as pills or purging.
- Perfectionism- found across EDs. Strober et al (2006) Evaluated AN teens getting treatment and found perfectionism common in 73% Females and 50% males. Potential genetic transmission of perfectionism and therefore vulnerability for AN.
- Impulsiveness- closer links with BN. AN act more impulsively than is self-reported. Montgomery (2005) compared to control group AN responded rapidly (innacurately) to a performance task
Eating disorders- AN Psych Eval
Case studies- difficult to generalise to a wider population, they could be individual situations.
Lack of solid evidence for media. AN still exists in non-western civilisations. Hoek et al (1998) Found in Curacao, Caribbean island where overweight is acceptable, 6 cases of AN still existed (at the same rate as western countries) Many studies find no signif differences between cultures.
Correlation is not usually found with peers and AN.
Ethical issues in testing what causes AN: if you are risking causing AN to pps- Becker
- Evo- deterministic
- Psychodynamic- unscientific
- Behavioural- reductionist
- Personality- Problems separating out lasting personality traits from short lived ones may be caused by starvation.
Combination of theories (Diathesis-stress) Connan et al (2003) AN has a genetic disposition that can be triggered by social and behavioural influences. Combining psychological with biological seems to account for various prevalences across the world.